Magnetic stack including cooling element

ABSTRACT

Various embodiments of a magnetic stack are disclosed. In one or more embodiments, the magnetic stack includes first and second shield layers, and a magnetically responsive lamination disposed between the first and second shield layers. The magnetically responsive lamination can be configured to receive a sense current I S  therethrough. The magnetic stack also includes a cooling element disposed between the first and second shield layers and thermally coupled to the magnetically responsive lamination. The cooling element can be configured to receive a bias current I B  therethrough. And the cooling element can be configured to cool the magnetically responsive lamination during a read function.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 15/045,563, filed Feb. 17, 2016, and which is a divisional of U.S.application Ser. No. 14/319,195, filed Jun. 30, 2014, now U.S. Pat. No.9,269,379, the disclosures of which are incorporated herein by referencethereto.

SUMMARY

In general, the present disclosure provides various embodiments of amagnetic stack that includes one or more cooling elements and a methodof using the stack.

In one aspect, the present disclosure provides one embodiment of amagnetic stack that includes first and second shield layers, and amagnetically responsive lamination disposed between the first and secondshield layers. The magnetically responsive lamination is configured toreceive a sense current I_(S) therethrough. The magnetic stack alsoincludes a cooling element disposed between the first and second shieldlayers and thermally coupled to the magnetically responsive lamination.The cooling element is configured to receive a bias current I_(B)therethrough. And the cooling element is configured to cool themagnetically responsive lamination during a read function.

In another aspect, the present disclosure provides another embodiment ofa magnetic stack that includes first and second shield layers, and amagnetically responsive lamination disposed between the first and secondshield layers. The magnetically responsive lamination is configured toreceive a sense current I_(S) therethrough. The magnetic stack alsoincludes an array of cooling elements thermally coupled to themagnetically responsive lamination. The array of cooling elements isconfigured to receive a bias current I_(B) therethrough. And the arrayof cooling elements is configured to cool the magnetically responsivelamination.

In another aspect, the present disclosure provides one embodiment of amethod that includes reading a selected data pattern from a storagemedium of a storage device using a head of the storage device to providea data signal; calculating an instability value of the head based on thedata signal; and applying a bias current I_(B) to a cooling elementthermally coupled to the head if the instability value is greater thanan instability threshold, where the cooling element is disposed betweenfirst and second shield layers of the head.

These and other aspects of the present disclosure will be apparent fromthe detailed description herein. In no event, however, should the abovesummaries be construed as limitations on the claimed subject matter,which subject matter is defined solely by the attached claims, as may beamended during prosecution.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the specification, reference is made to the appendeddrawings, where like reference numerals designate like elements, andwherein:

FIG. 1 is a schematic perspective view of one embodiment of a datastorage device.

FIG. 2 is a schematic cross-section view of one embodiment of a magneticstack.

FIG. 3 is a schematic cross-section view of one embodiment of amagnetically responsive lamination.

FIG. 4 is a schematic cross-section view of one embodiment of a coolingelement.

FIG. 5 is a schematic cross-section view of another embodiment of amagnetic stack.

FIG. 6 is a schematic cross-section view of another embodiment of amagnetic stack.

FIG. 7 is a schematic cross-section view of another embodiment of amagnetic stack.

FIG. 8 is a flow diagram of one embodiment of a method of cooling amagnetically responsive lamination of a magnetic stack.

DETAILED DESCRIPTION

In general, the present disclosure provides various embodiments of amagnetic stack that can include one or more cooling elements and amethod of using the stack.

Electronic devices, e.g., solid-state devices, can be affected bythermal fluctuations or increased temperatures. For example, read/writeheads utilized in data storage devices can experience performancedegradation under elevated temperatures that can occur during normaloperation. In such devices, various elements and techniques can beutilized to mitigate this thermal degradation.

For example, one or more embodiments of magnetic stacks of the presentdisclosure can include a cooling element that can reduce the temperaturein one or more portions of the magnetic head. Such cooling can helpmitigate thermal instability of the head. Further, in one or moreembodiments, the cooling element can be actively controlled to providecooling during any suitable function of the magnetic stack, e.g., one orboth of a read function and a write function.

Heads can include one or more heaters that can control a fly heightbetween the head and a storage medium. For example, a heater associatedwith a read element of a head can be used to change the fly heightbetween the read element and the storage medium. Such a heater, however,can cause elevated temperatures in and around the read element. Further,heating of the head can be caused by power losses from conductioncurrent driven by a sense current that is provided through the head forcreating a signal from the head. Subsequently, performance degradationduring operation at elevated temperatures can be caused by both of thesemechanisms or other mechanisms as well. Such degradation can includeside-shield free layer magnetic bias, thermally promoted grain switchingof one or both of synthetic anti-ferromagnetic (SAF) layers andantiferromagnetic (AFM) layers, thermally promoted grain switching neardefects in shields, and associated noise increases leading to reducedsignal-to-noise ratio (SNR).

In general, the present disclosure provides one or more embodiments of amagnetic stack and devices that include such magnetic stacks, e.g., datastorage devices. In one or more embodiments, the magnetic stack caninclude first and second shield layers; a magnetically responsivelamination disposed between the first and second shield layers; and acooling element disposed between the first and second shield layers andthermally coupled to the magnetically responsive lamination. The coolingelement can be configured to cool the magnetically responsivelamination.

An example of a data storage device 10 is provided in FIG. 1. The device10 shows a non-limiting environment in which various embodiments of thepresent disclosure can be practiced. The device 10 includes asubstantially sealed housing 12 formed from a base deck 14 and top cover16. An internally disposed spindle motor 18 is configured to rotate oneor more of magnetic storage media 20. The media 20 are accessed by acorresponding array of data transducers (read/write heads) that are eachsupported by a head gimbal assembly (HGA) 22.

Each HGA 22 can be supported by a head-stack assembly 24 (“actuator”)that includes a flexible suspension 26, which in turn is supported by arigid actuator arm 28. The actuator 24 preferably pivots about acartridge bearing assembly 30 through application of current to a voicecoil motor (VCM) 32. In this way, controlled operation of the VCM 32causes the transducers (numerically denoted at 34) or head to align withtracks (not shown) defined on the media surfaces to store data theretoor retrieve data therefrom.

FIG. 2 is a schematic cross-section view of one embodiment of a magneticstack 40 capable of being used, e.g., as a read element or sensor in thedata transducers 34 of FIG. 1. As illustrated, the magnetic stack 40includes a first shield layer 42 and a second shield layer 44, and amagnetically responsive lamination 46 disposed between the first andsecond shield layers. The magnetically responsive lamination 46 can, inone or more embodiments, be separated from a sensed data bit 48 storedin an adjacent medium 50 by an air bearing surface 52 (ABS). The stack40 also includes a cooling element 56 disposed between the first andsecond shield layers 42, 44.

The first and second shield layers 42, 44 can each include any suitablematerial or combination of materials. In one or more embodiments, atleast one of the first and second shield layers 42, 44 can include anysuitable material or combination of materials such that the shieldlayers shield the magnetically responsive lamination 46 from straymagnetic fields, e.g., NiFe, CoNiFe, etc. In one or more embodiments,the first shield layer 42 and second shield layer 44 can include thesame materials; in other embodiments, the first shield layer includesmaterial or materials that are different from the material or materialsof the second shield layer. Further, the first and second shield layers42, 44 can take any suitable shape or combination of shapes and have anysuitable dimensions. Shielding by the first and second shield layers 42,44 can allow for improved magnetic sensing of programmed bits 48 frommedium 50 by eliminating noise and inadvertent sensing of adjacent bits.

Disposed between the first and second shield layers 42, 44 is themagnetically responsive lamination 46. Although referred to as alamination, the magnetically responsive lamination 46 can be formedusing any suitable technique or combination of techniques. In one ormore embodiments, the magnetically responsive lamination 46 isconfigured to receive a sense current I_(S) 66 therethrough as isfurther described herein.

The lamination 46 can include any suitable construction such that, inone or more embodiments, the lamination is capable of being used as aread element or sensor in a head of a data storage device (e.g., device10 of FIG. 1). For example, FIG. 3 is a schematic cross-section view ofone embodiment of a magnetically responsive lamination 70. Themagnetically responsive lamination 70 includes a ferromagnetic freelayer 72, a synthetic antiferromagnetic (SAF) structure 74, and a firstspacer layer 76 positioned between the free layer and the SAF structure.In one or more embodiments, the magnetically responsive lamination 70can include any suitable layer or layers.

In the illustrated embodiment, the magnetically responsive lamination 70includes the free layer 72 that can be sensitive to external magneticfields. That is, the free layer 72 can have a magnetization thatcorresponds to an encountered external magnetic field, such as providedby programmed sensed data bits 48 on the adjacent storage medium 50 (asillustrated in FIG. 2). The free layer 72 can include any suitablematerial or combination of materials, e.g., NiFe, CoFe, CoNiFe, CoFeB,magnetic Heusler alloys, etc.

The SAF structure 74 of the lamination 70 is separated from the freelayer 72 by the first spacer layer 76. The SAF structure 74 can have apredetermined set magnetization. In the embodiment illustrated in FIG.3, the SAF structure 74 includes a reference layer 78, and anon-magnetic second spacer layer 82 positioned between the referencelayer and a pinned layer 80. In other embodiments, the SAF structure 74can include any suitable layer or layers. For example, the SAF structure74 can include a lamination of a transition metal, such as Ru, disposedbetween ferromagnetic crystalline or amorphous sub-layers, such asmetals like Ni and Co, alloys like CoFe and NiFe, and high polarizationratio compounds like CoFeB. The reference layer 78 can include anysuitable material or combination of materials, e.g., CoFe, CoFeB, etc.

The second spacer layer 82 can include any suitable material orcombination of materials, e.g., Ru, and can have any suitable thicknessto accommodate free layer magnetic sensing.

The free layer 72 and SAF structure 74 can each be coupled to anelectrode layer, e.g., one or more seed layers, cap layers, etc., thatprovide both manufacturing and operational improvements. It should benoted, however, that the composition, shape, and placement of theelectrode layers are not limited and can be modified or removed.

The pinned layer 80 is positioned between the second spacer layer 82 andan optional AFM structure (e.g., AFM structure 60 of FIG. 2). In one ormore embodiments, the pinned layer 80 is coupled to the AFM structure.Further, in one or more embodiments, the pinned layer 80 can be coupledto a shield layer (e.g., first shield layer 42 of FIG. 2). The pinnedlayer 80 can include any suitable material or combination of materials,e.g., Co, CoFe, CoFeB, etc.

Positioned between the free layer 72 and the SAF structure 74 is thefirst spacer layer 76. The first spacer layer 76 can include anysuitable material or combination of materials, e.g., Co, Ag, MgO, TiO,Al₂O₃, etc. In one or more embodiments, the first spacer layer 76 caninclude the same material as the second spacer layer 82.

Returning to FIG. 2, the stack 40 can include a current source 54 thatis configured to provide the sense current I_(S) 66 through themagnetically responsive lamination 46. The current source 54 can includeany suitable circuitry or devices to provide sense current I_(S).Further, the current source 54 can be electrically coupled to anysuitable element of the stack 40 to provide sense current I_(S) to thelamination 46. For example, in the embodiment illustrated in FIG. 2, thecurrent source 54 is electrically coupled to the first shield layer 42and the cooling element 56. In one or more alternative embodiments, thecurrent source 54 can be electrically coupled to AFM layer 60 and thecooling element 56. In one or more alternative embodiments, the stack 40can include any suitable additional layer or layers that areelectrically coupled to the current source 54 to provide sense currentI_(S) through the lamination 46. The sense current I_(S) can be directedthrough the magnetically responsive lamination 46 and magnetic flux canbe detected by measuring the change in voltage across the lamination 46as a function of changing resistivity.

Further, the current source 54 can be oriented in any suitable manner.For example, as illustrated, the positive side of the current source 54can be electrically coupled to the first shield layer 42, and thenegative side of the current source can be electrically coupled to thecooling element 56. Alternatively, in one or more embodiments, thepositive side of the current source 54 can be electrically coupled tothe cooling element 56, and the negative side of the current source canbe electrically coupled to the first shield layer 42.

Also disposed between the first and second shield layers 42, 44 is thecooling element 56. Although depicted as including one cooling element56, the magnetic stack 40 can include any suitable number of coolingelements as is further described herein. In one or more embodiments, thecooling element 56 is thermally coupled to the magnetically responsivelamination 46. Further, in one or more embodiments, the cooling element56 can also be thermally coupled to the second shield layer 44.

The cooling element 56 can be disposed in any suitable location. Forexample, in one or more embodiments, the cooling element 56 can bedisposed between the magnetically responsive lamination 46 and the firstshield layer 42. In one or more alternative embodiments, the coolingelement 56 can be disposed between the magnetically responsivelamination 46 and the second shield layer 44 as is illustrated in FIG.2. In one or more alternative embodiments, the cooling element 56 can bedisposed next to or beside the magnetically responsive lamination 46such that the lamination 46 is between the cooling element and the ABS52. As is further described herein, in one or more embodiments,insulating material can be disposed between the cooling element 56 andthe ABS 52. In one or more alternative embodiments, the cooling element56 can be disposed proximate the magnetically responsive lamination 46.As used herein, the phrase “proximate the magnetically responsivelamination” means that the cooling element 56 is positioned such that itis thermally coupled to the magnetically responsive lamination 46.Although not shown, the cooling element 56 can be electrically isolatedfrom the rest of the stack 40 using any suitable insulating material.

In one or more embodiments, the cooling element 56 can be disposed suchthat it is in contact with the magnetically responsive lamination 46. Inone or more alternative embodiments, one or more layers can be disposedbetween the cooling element 56 and the magnetically responsivelamination 46.

The cooling element 56 can include any suitable construction such thatit is operable to reduce the temperature of (i.e., cool) themagnetically responsive lamination 46 and/or a head of a storage device.In one or more embodiments, the cooling element 56 can include a Peltiercooling element. A Peltier cooling element is a device or structure thatutilizes the Peltier Effect, which occurs when an electrical current issent through two dissimilar materials that are physically orelectrically connected to one another at one or more junctions. Onejunction between the two materials becomes warm while the other becomescool in what amounts to an electrically driven transfer of heat from oneside of the device to the other. The Peltier heat generated at thejunction per unit time, {dot over (Q)}, is equal to{dot over (Q)}=(Π_(A)−Π_(B))Iwhere Π_(A)(Π_(B)) is the Peltier coefficient of conductor A(B), and Iis the electric current (from A to B). The Peltier coefficientsrepresent how much heat is carried per unit charge. A typical Peltiercooling element can include multiple junctions in series through which acurrent is driven. Some of the junctions lose heat due to the Peltiereffect, while others gain heat.

For example, FIG. 4 is a schematic cross-section view of one embodimentof a Peltier cooling element 90. The cooling element 90 includes firstand second materials 94, 96. The first and second materials 94, 96 areseparated by a third material 98. A current source 92 is electricallycoupled to the first and second materials 94, 96 to supply current tothe element 90.

The materials used for the first, second, and third materials 94, 96, 98are, in one or more embodiments, different conducting materials havingdifferent electron densities. When an electrical conductor connectsfirst, second, and third materials 94, 96, 98 to each other, a newequilibrium of free electrons will be established. Potential migrationcreates an electrical field across each of the connections. When currentis subsequently forced through the element 90, the attempt to maintainthe new equilibrium causes the electrons at one connection to absorbenergy and those at the other connection to release energy. The greaterthe difference between Seebeck coefficients of the first, second, andthird materials 94, 96, 98 at each of the junctions between the threematerials, the greater the Peltier effect and thus, the device 90 canprovide greater cooling. This results in a cool end or side and a hotend or side of the device 90.

The first, second, and third materials 94, 96, 98 can include anysuitable material or combination of materials. For example, in one ormore embodiments, at least one of the first, second, and third materials94, 96, 98 can include metals and/or semiconductor materials. The use ofmetals allow for processing convenience at a lower Seebeck coefficient(Π=TS, where S is the Seebeck coefficient, Π is the Peltier coefficient,and T is the temperature), whereas the use of semiconductors provideshigher Seebeck coefficients and, therefore, higher cooling capacity.Table I includes exemplary materials and their corresponding Seebeckcoefficients.

TABLE 1 Material Seebeck Coefficient (uV/K) Metal Antimony 47 Nichrome25 Molybdenum 10 Tungsten 7.5 Gold 6.5 Silver 6.5 Copper 6.5 Tantalum4.5 Aluminum 3.5 Platinum 0 (reference) Nickel −15 Semiconductor Se 900Te 500 Si 440 Si (B-doped) 1266 Si (Ar-doped) −1333 Ge 300 GaN 300 PbTe−180 GaAs ~−500 Dichalcogenides Carbon 100−10⁴ (graphene, 2D) MoS₂ (2D)>−10⁵ WS₂ (2D) 500-600 WSe (2D) ~600 MoSe₂ (2D) 0-200 Heusler AlloysCo₂TiAl −55 Co₂TiSi −27 Co₂TiGe −22 Co₂TiSn −34 Co₂MnAl −4 Co₂MnSi −7Co₂MnGe −15 Co₂MnSn −33 Co₂FeSi −12

In one or more embodiments, at least one of the first, second, and thirdmaterials 94, 96, 98 can include a Huesler alloy, e.g., alloys having achemical formula of A₂BC, where A includes Co, Ir, Rh, Pt, Cu, Ni, Pd,and combinations thereof, B includes V, Cr, Mn, Fe, and Ti, and Cincludes Al, Si, Ga, Sn, and Ge. Exemplary Huesler alloys include thoselisted in Table 1.

In one or more embodiments, one or more of the first, second, and thirdmaterials 94, 96, 98 can include a combination of two or more Heusleralloys.

In one or more embodiments, the first, second, and third materials 94,96, and 98 can be selected to provide desired magnetic properties of thecooling element 90 when the element 90 is included in a magnetic stack,e.g., stack 40 of FIG. 2.

Returning to FIG. 2, the cooling element 56, in one or more embodiments,can be configured to receive a bias current I_(B) 68 therethrough. Thebias current 68 can be provided to the cooling element 56 such that theelement can cool the magnetically responsive lamination 46 as is furtherdescribed herein.

In one or more embodiments, the bias current I_(B) can be equal to thesense current I_(S). In one or more alternative embodiments, the biascurrent I_(B) can be different from the sense current I_(S). In one ormore embodiments, cooling element 56 can be controlled independentlyfrom the magnetically responsive lamination 46. In other words, the biascurrent I_(B) can be controlled independently from the sense currentI_(S). The bias current I_(B) can be any suitable current. In one ormore embodiments, the bias current I_(B) can be greater than 0 amps. Inone or more embodiments, the bias current I_(B) can be less than 1 amp.

As illustrated in FIG. 2, the bias current I_(B) 68 can be provided bycurrent source 58. Any suitable circuitry or devices can be utilized ascurrent source 58. The current source 58 can be electrically coupled tothe cooling element 56 in any suitable manner such that the bias currentI_(B) can be provided through the cooling element. For example, in theembodiment illustrated in FIG. 2, the current source 58 is electricallycoupled to the second shield layer 44 and the cooling element 56, andthe second shield layer is electrically coupled to the cooling elementsuch that the bias current I_(B) can be directed through the coolingelement. In one or more alternative embodiments, the current source 58can be electrically coupled directly to the cooling element 56 and notthe second shield layer 44.

Further, the current source 58 can be configured such that it providescurrent to the cooling element 56 in any suitable orientation. Forexample, as illustrated in FIG. 2, the positive side of the currentsource 58 is electrically coupled to the second shield layer 44, and thenegative side of the current source is electrically coupled to thecooling element 56. In one or more alternative embodiments, the positiveside of the current source 58 can be electrically coupled to the coolingelement 56, and the negative side of the current source can beelectrically coupled to the second shield layer 44.

The cooling element 56 can be configured to reduce the temperature of(i.e., cool) the magnetically responsive lamination 46 during anyfunction or cycle of a storage device. In one or more embodiments, thecooling element 56 can be configured to cool the magnetically responsivelamination 46 during a read function when the lamination is beingutilized to sense data stored in medium 50. During read functions, atemperature of the lamination 46 can increase as the sense current I_(S)66 is directed through the lamination. Further, during read functions, aheater associated with the lamination 46 can increase a temperature of aportion of the stack 40 near or proximate the lamination 46 to reducethe fly height between the stack and the magnetic medium 50. Cooling thelamination 46 during the read function when power to the heaterassociated with the lamination is increased can, in one or moreembodiments, reduce thermal instability of the lamination.

In one or more embodiments, the cooling element 56 is configured to coolthe magnetically responsive lamination 46 during a write function of thestorage device. And in one or more embodiments, the cooling element 56is configured to cool the magnetically responsive lamination 46 duringboth a read function and a write function of the storage device.Further, in one or more embodiments, the cooling element 56 can beconfigured to cool the magnetically responsive lamination 46 betweenread and write functions.

The magnetic stack 40 can also include a controller 62 operably coupledto the stack. In one or more embodiments, the controller 62 is operableto control the bias current I_(B) 68. In one or more embodiments, thecontroller 32 can also be utilized to control the sense current I_(S).Any suitable controller or controllers can be utilized to control one orboth of the bias current I_(B) and the sense current I_(S).

The methods, techniques, and/or processes described in this disclosure,including those attributed to the controller, or various constituentcomponents, may be implemented, at least in part, in hardware, software,firmware, or any combination thereof. For example, various aspects ofthe techniques may be implemented within one or more controllers,including one or more microprocessors, digital signal processors (DSPs),application specific integrated circuits (ASICs), field programmablegate arrays (FPGAs), or any other equivalent integrated or discretelogic circuitry, as well as any combinations of such components. Theterm “processing apparatus,” “processor,” or “processing circuitry” maygenerally refer to any of the foregoing logic circuitry, alone or incombination with other logic circuitry, or any other equivalentcircuitry.

Such hardware, software, and/or firmware may be implemented within thesame device or within separate devices to support the various operationsand functions described in this disclosure. In addition, any of thedescribed units, modules, or components may be implemented together orseparately as discrete but interoperable logic devices. Depiction ofdifferent features as modules or units is intended to highlightdifferent functional aspects and does not necessarily imply that suchmodules or units must be realized by separate hardware or softwarecomponents. Rather, functionality associated with one or more modules orunits may be performed by separate hardware or software components, orintegrated within common or separate hardware or software components.

When implemented in software, the functionality ascribed to the systems,devices and techniques described in this disclosure may be embodied asinstructions on a computer-readable medium such as RAM, ROM, NVRAM,EEPROM, FLASH memory, STRAM, RRAM, magnetic data storage media, opticaldata storage media, or the like. The instructions may be executed by oneor more processors to support one or more aspects of the functionalitydescribed in this disclosure.

The magnetic stack 40 can also include an optional AFM structure 60disposed in any suitable location between the first and second shieldlayers 42, 44. In the illustrated embodiment, the AFM structure 60 ispositioned between the magnetically responsive lamination 46 and thefirst shield layer 42. The AFM structure 60 can include any suitablelayer or layers having any suitable material or materials. For example,in one or more embodiments, the AFM structure 60 can include an AFMlayer, a first seed layer, and a second seed layer positioned betweenthe AFM layer and the first seed layer. In one or more embodiments, suchan AFM layer can be coupled to the pinned layer of an SAF structure(e.g., pinned layer 80 of SAF structure 74 of FIG. 3).

In one or more embodiments, the magnetic stack 40 can include one ormore additional layers that provide various functions. For example, FIG.5 is a schematic cross-section view of one embodiment of a magneticstack 120 that includes third shield layer 150. All of the designconsiderations and possibilities regarding the magnetic stack 40 of FIG.2 apply equally to the magnetic stack 120 of FIG. 5.

The magnetic stack 120 includes first and second shield layers 122, 124,and a magnetically responsive lamination 126 disposed between the firstand second shield layers. In one or more embodiments, the magneticallyresponsive lamination 126 is separated from a sensed data bit 128 storedin an adjacent medium 130 by an ABS 132. The magnetically responsivelamination 126 is configured to receive a sense current I_(S) 146therethrough. The stack 120 also includes a cooling element 136 disposedbetween the first and second shield layers 122, 124. In one or moreembodiments, the cooling element 136 is thermally coupled to themagnetically responsive lamination 126. Further, in one or moreembodiments, the cooling element 136 is configured to receive a biascurrent I_(B) 148 therethrough. And in one or more embodiments, thecooling element 136 is configured to cool the magnetically responsivelamination 126 during any suitable function or cycle of a magneticstorage device, e.g., during a read function.

As illustrated in FIG. 5, the third shield layer 150 is disposed suchthat the cooling element 136 is between the third shield layer and thesecond shield layer 124, where the third shield layer is magneticallycoupled to the second shield layer and electrically coupled to thecooling element. The third shield layer 150 can include any suitablematerial or combination of materials, e.g., the same material ormaterials described in reference to first and second shield layers 42,44 of stack 40 of FIG. 2.

The third shield layer 150 can be electrically coupled to the coolingelement 136 such that the third shield layer can provide an electrode orcontact for current source 138 that provides bias current I_(B) throughthe cooling element. In other words, the third shield layer 150 acts asan electrode for cooling element 136. In one or more embodiments, thecurrent source 138 is electrically coupled to the second shield layer124 to provide another electrode for the cooling element 136.Alternatively, in one or more embodiments, separate electrode layers canbe disposed between the second shield layer 124 and the cooling element136 and/or between the cooling element and the third shield layer 50 toelectrically couple the current source 138 to the cooling element.

As mentioned herein, the cooling elements of the present disclosure canbe disposed in any suitable location relative to a magneticallyresponsive lamination such that the cooling element can cool thelamination. For example, FIG. 6 is a schematic cross-section view ofanother embodiment of a magnetic stack 160. All of the designconsiderations and possibilities regarding the magnetic stack 40 of FIG.2 apply equally to the magnetic stack 160 of FIG. 6. One differencebetween the magnetic stack 160 and the magnetic stack 40 is that thecooling element 162 is positioned such that electrically insulatingmaterial 164 is disposed between the cooling element and ABS 166.Although not wishing to be bound by any particular theory, providinginsulating material 164 between the cooling element 162 and the ABS 166may help electrically shield magnetically responsive lamination 168 fromnoise that may be created by current that is directed through thecooling element. The insulating material 164 can include any suitablematerial or combination of materials and include any suitabledimensions.

Although stack 40 of FIG. 2 includes a single cooling element 56, in oneor more embodiments, the stack can include two or more cooling elements.For example, FIG. 7 is a schematic cross-section view of one embodimentof a magnetic stack 170. All of the design considerations andpossibilities regarding the magnetic stack 40 of FIG. 2 apply equally tomagnetic stack 170 of FIG. 7. One difference between magnetic stack 170and magnetic stack 40 is that stack 170 includes an array of coolingelements 178 disposed between first and second shield layers 172, 174.As illustrated in FIG. 7, the array of cooling elements 178 is thermallycoupled to magnetically responsive lamination 176 and is configured toreceive a bias current I_(B) (not shown) therethrough. The array ofcooling elements 178 is also configured to cool the magneticallyresponsive lamination 176.

The array of cooling elements 178 can include any suitable number ofcooling elements. Further, the array of cooling elements 178 can includeany suitable cooling element or elements. The individual elements of thearray of cooling elements 178 can be electrically connected in anysuitable manner, e.g., in serial or parallel configurations. In one ormore embodiments, the individual elements of the array of coolingelements 178 can be independently controllable using any suitabletechnique or combination of techniques. For example, a controller 180can be utilized to independently control one or more of the individualelements of the array of cooling elements 178. In one or moreembodiments, independently controllable elements of the array of coolingelements 178 can provide selected cooling zones for the magneticallyresponsive lamination 176.

The cooling elements of the array of cooling elements 178 can beconfigured in any suitable configuration or array. In one or moreembodiments, the cooling elements of the array of cooling elements 178can be configured such that each cooling element lies in a plane that issubstantially parallel to a plane that contains the second shield layer174. Further, each cooling element of the array of cooling elements 178can be oriented in any suitable position. For example, in one or moreembodiments, one or more cooling elements can be configured and orientedsuch that the bias current I_(B) flows through the element in adirection substantially parallel to an air bearing surface (ABS) 182 ofthe stack 170. Alternatively, in one or more embodiments, one or morecooling elements can be configured and oriented such that the biascurrent I_(B) flows through the element in a direction substantiallytransverse to the ABS 182.

In general, the magnetic stacks of the present disclosure can bemanufactured using any suitable technique or combination of techniques,e.g., sputter deposition, chemical vapor deposition, epitaxialdeposition, etc. In one or more embodiments, the magnetic stack can bevertically integrated. Such vertically integrated stacks can bemanufactured using any suitable technique or combination of techniques,e.g., sputter deposition, chemical vapor deposition, epitaxialdeposition, etc.

Any suitable technique or combination of techniques can be utilized tocontrol the cooling elements of the present disclosure. For example,FIG. 8 is a flow diagram of one embodiment of a method 200 ofcontrolling a cooling element of a magnetic stack (e.g., stack 40 ofFIG. 2). The stack can be utilized, e.g., as a read element of a head ofa storage device (e.g., device 10 of FIG. 1). In general, an instabilityvalue of a head of a storage device can be determined or calculatedbased on any suitable data signal of the device. For example, a selecteddata pattern stored on a storage medium of a storage device can be readto provide a data signal from which an instability value (e.g., thermalinstability value) can be calculated. This instability value can becompared to an instability threshold, and a bias current I_(B) can beapplied to the cooling element (e.g., cooling element 56 of FIG. 2) ifthe instability value is greater than an instability threshold.

Specifically, in reference to magnetic stack 40 of FIG. 2, the coolingelement 56 can be controlled by reading a selected data pattern toprovide a data signal 202. Such data pattern can be stored or written ona suitable media e.g. magnetic storage media 20 of FIG. 1. Any suitabledata pattern can be written to a storage medium.

The selected pattern can be read from the storage medium using the headto provide the data signal 202. Any suitable technique or combination oftechniques can be used to read the selected pattern. For example, in oneor more embodiments, reading the selected pattern can include multiplerevolutions and senses of the pattern (e.g., about 20 senses, about 30senses, about 40 senses, etc.), and each of the senses can be averagedto provide the data signal. In one or more embodiments, the selectedpattern can be read for a selected number of reads over a selected timeperiod. The selected number of reads can be between about 25 reads toabout 500 reads. In one or more embodiments, the selected number ofreads can be greater than or equal to about 25 reads, about 40 reads,about 50 reads, about 60 reads, about 70 reads, about 80 reads, about 90reads, about 100 reads, about 125 reads, about 150 reads, about 200reads, about 250 reads, etc. In one or more embodiments, the selectednumber of reads can be less than or equal to about 500 reads, about 400reads, about 300 reads, about 250 reads, about 200 reads, about 175reads, about 150 reads, about 125 reads, about 100 reads, about 90reads, about 75 reads, about 50 reads, etc.

Additionally, the selected number of reads may be described based on arate. In one or more embodiments, the selected pattern can be readbetween about 1 time per minute to about 100 times per minute. In one ormore embodiments, the pattern may be read greater than or equal to about1 time per minute, about 2 times per minute, about 3 times per minute,about 5 times per minute, about 10 times per minute, about 15 times perminute, about 20 times per minute, about 30 times per minute, about 40times per minute, about 50 times per minute, about 60 times per minute,etc. In one or more embodiments, the selected pattern can be read lessthan or equal to about 100 times per minute, about 90 times per minute,about 80 times per minute, about 70 times per minute, about 60 times perminute, about 50 times per minute, about 40 times per minute, about 30times per minute, about 25 times per minute, about 20 times per minute,about 15 times per minute, etc.

An instability value 204 of the head is calculated based on the datasignal 202. The instability value 204 can be calculated using anysuitable technique or combination of techniques. For example, in one ormore embodiments, a bit error rate of the data signal can be determinedto provide an instability value. Any suitable technique or combinationof techniques can be used to determine the bit error rate of the datasignal.

In one or more embodiments, an instability value 204 of the entirestorage device can be calculated. In one or more alternativeembodiments, an instability value 204 for each head of the storagedevice can be calculated. For example, because the characteristics(e.g., thermal characteristics) of each head may be unique, for devicesthat include two or more heads (e.g., one head per storage medium fordevices that include two or more storage media, multiple heads for eachstorage medium, etc.), an instability value 204 for each head can becalculated.

The instability value 204 can be compared to an instability threshold206. Any suitable instability threshold 206 can be utilized. In one ormore embodiments, the instability threshold can include a standarddeviation of the bit error rate (BER) of the device.

If the instability value 206 of the head of the device is equal to orless than the desired instability threshold 204, then testing proceedsto any desired additional testing or functioning states at 208, e.g.,the device or system can perform further testing or can end testing andbegin typical read/write routines or functions for reading and/orwriting data to and from a storage medium. If, however, the instabilityvalue 204 is greater than the desired instability threshold 206, then abias current I_(B) 210 provided to the cooling element 56 that isthermally coupled to the magnetically responsive lamination 46 can beapplied. The method can proceed to any suitable next states 212, e.g.,further testing 202 or typical read/write functions. In one or moreembodiments, if the instability value 204 continues to exceed thedesired instability threshold 206, then the bias current I_(B) 210 canbe increased. Further, in one or more embodiments, if the instabilityvalue 204 is less than the desired instability threshold 206 while thebias current I_(B) is being provided to the cooling element 56, then thebias current I_(B) can be decreased to a desired level.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the properties sought tobe obtained by those skilled in the art utilizing the teachingsdisclosed herein.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, and 5) and any range within that range.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise. As used inthis specification and the appended claims, the term “or” is generallyemployed in its sense including “and/or” unless the content clearlydictates otherwise.

“Include,” “including,” or like terms means encompassing but not limitedto, that is, including and not exclusive. It should be noted that “top”and “bottom” (or other terms like “upper” and “lower”) are utilizedstrictly for relative descriptions and do not imply any overallorientation of the article in which the described element is located.

All references and publications cited herein are expressly incorporatedherein by reference in their entirety into this disclosure, except tothe extent they may directly contradict this disclosure. Illustrativeembodiments of this disclosure are discussed and reference has been madeto possible variations within the scope of this disclosure. These andother variations and modifications in the disclosure will be apparent tothose skilled in the art without departing from the scope of thedisclosure, and it should be understood that this disclosure is notlimited to the illustrative embodiments set forth herein. Accordingly,the disclosure is to be limited only by the claims provided below.

What is claimed is:
 1. A method comprising: reading a selected datapattern from a storage medium of a storage device using a head of thestorage device to provide a data signal; calculating an instabilityvalue of the head based on the data signal; and applying a bias currentI_(B) to a cooling element thermally coupled to the head if theinstability value is greater than an instability threshold, wherein thecooling element is disposed between first and second shield layers ofthe head.
 2. The method of claim 1, wherein reading data from thestorage medium comprises providing a sense current I_(S) to the head,wherein I_(S) and I_(B) are independently controllable.
 3. The method ofclaim 1, wherein calculating the instability value comprises determininga bit error rate of the data signal.
 4. The method of claim 1, whereincalculating the instability value comprises calculating an instabilityvalue for each head of the storage device.
 5. The method of claim 1,wherein the instability threshold comprises a standard deviation of abit error rate of the device.
 6. The method of claim 1, furthercomprising writing additional data to the storage medium if theinstability value of the head is less than or equal to the instabilitythreshold.
 7. The method of claim 1, further comprising decreasing thebias current I_(B) if the instability value is less than the instabilitythreshold.
 8. The method of claim 1, wherein the head further comprisesa magnetically responsive lamination disposed between the first andsecond shield layers and configured to receive a sense current I_(S)therethrough, wherein the cooling element is thermally coupled to themagnetically responsive lamination.
 9. The method of claim 8, whereinthe cooling element is disposed between the magnetically responsivelamination and the second shield layer.
 10. The method of claim 8,wherein the cooling element is in contact with the magneticallyresponsive lamination.
 11. The method of claim 8, wherein themagnetically responsive lamination comprises a ferromagnetic free layer,a synthetic antiferromagnetic (SAF) structure, and a spacer layerpositioned between the ferromagnetic free layer and the SAF structure.12. The method of claim 8, wherein the head further comprises anantiferromagnetic (AFM) structure disposed between the first shieldlayer and the magnetically responsive lamination and magneticallycoupled to the magnetically responsive lamination.
 13. The method ofclaim 1, wherein the cooling element comprises a Peltier coolingelement.
 14. The method of claim 1, wherein the head further comprisesinsulating material disposed between the cooling element and an airbearing surface (ABS) of the magnetic stack.
 15. The method of claim 1,wherein the cooling element comprises an array of cooling elements. 16.The method of claim 15, wherein each cooling element of the array ofcooling elements is independently controllable.
 17. The method of claim1, wherein reading the selected data pattern comprises sensing the datapattern a plurality of senses and averaging the plurality of senses toprovide the data signal.
 18. The method of claim 1, wherein reading theselected data pattern comprises reading the selected data patternbetween about 1 time per minute to about 100 times per minute to providethe data signal.